Composite Articles Comprising Protective Sheets and Related Methods

ABSTRACT

Methods of the invention include those for applying protective sheets to composite articles. According to these methods and resulting composite articles, a protective sheet is applied to at least a portion of an exterior surface formed from a composite material and where protection is desired. At least one exterior surface of the composite article to be protected can be integrally formed in the presence of the protective sheet. Improved bonding of the protective sheet to the composite article and improved processing efficiency are advantageously achieved according to the invention.

BACKGROUND OF THE INVENTION

The present invention relates generally to composite articles made fromcomposite materials and which comprise protective sheets, as well asmethods of making and using the same.

A variety of protective sheets and protective coatings can beselectively applied to protect exterior surfaces on a variety ofarticles. Often, protective sheets and protective coverings areselectively applied to an article's surface after the article is formed.Many such applications are intended to reduce abrasion or other wear onthe underlying surface. Other applications are geared primarily towardmaintaining or improving aesthetics or integrity of an underlyingsurface (e.g., when the underlying surface contains printed materialthereon or when the surface contains aesthetically undesirable pinholes,bubbles, or other surface imperfections that can occur when, forexample, producing molded articles). It is not surprising that thereexists a need for protective sheets and protective coatings in a varietyof applications.

Certain protective sheets and protective coatings, as well as relatedmethods for making and using the same, are known. As an example,polyurethane “clearcoat” protective coatings have been applied to avariety of finished molded parts, such as plastic body panels, in orderto bolster weathering performance, as well as scratch- andabrasion-resistance, without detrimentally affecting appearance of theunderlying surface. Another example involves application of polyurethanesheets to automotive body panels for protection of the body panelagainst chipping or other damage caused by, for example, objects such asflying stones or debris. As another example, “leading edge tapes” havebeen applied to select portions of articles, such as helicopter bladesand aircraft noses or wings, in order to protect underlying surfacesfrom scratch- and abrasion-resistance.

When the underlying surface is made from a composite material (e.g., afiber-reinforced composite), surface protection often has multiple goalswithin a particular application. A wide variety of composite materialsand methods for their preparation and use are known. In the case of afiber-reinforced composite, a polymeric resin matrix and fibrousreinforcement together often form the composite. A variety of materialscan be used for each of the polymeric resin matrix and the fibrousreinforcement components. For example, materials useful for fibrousreinforcement include carbon fibers, boron fibers, and glass fibers.Further, examples of materials useful for the polymeric resin matrixinclude thermoplastics (e.g., nylon) and thermosets (e.g., epoxies andphenolics).

Composite materials are finding increased use in applications wherelightweight materials are desired and where an associated compromise instrength or stiffness of the material would likely be problematic. Manycomposite materials are also useful in applications where corrosionresistance is desired, as composite materials more often exhibitexcellent corrosion resistance as compared to alternative materials.

Due to their beneficial properties, a variety of specialized sportingimplements and other articles are increasingly being made from compositematerials. For example, composite materials are increasingly being usedin shaft-based sporting implements (i.e., those sporting implementshaving a generally elongated portion, which may or may not be hollow oruniform in thickness and shape throughout) and similar articles. Sucharticles include, for example, golf clubs, bicycle frames, hockeysticks, lacrosse sticks, skis, ski poles, fishing rods, tennis rackets,arrows, polo mallets, and bats. As an example, the use of compositematerials enables golf club manufacturers to produce shafts havingvarying degrees of strength, flexibility, and torsional stiffness.

In addition, a variety of articles in the transportation and energyindustries are increasingly being made from composite materials. Forexample, composite materials are often used to make various aerospacecomponents, such as wing and blade components, including those onhelicopters and specialized military aircraft. Further, compositematerials are often used to make various automotive components, bothinterior and exterior, including body panels, roofs, doors, gear shiftknobs, seat frames, steering wheels, and others. In the energy industry,composite materials are used to make wind mill blades—e.g., large windturbine blades are made more efficient through the use of carbonfiber-reinforced composites. Indeed, the number of current and potentialapplications for composite materials is extensive.

Beneficially, composite materials offer enhancements in strength,stiffness, corrosion resistance, and weight savings. These beneficialproperties are often balanced against competing relative weaknesses inabrasion resistance and impact resistance. In addition, as manycomposite articles are made by layering multiple, individual compositematerial layers to achieve the desired properties, such compositearticles are susceptible to interlayer delamination, particularly uponimpact. This is especially the case with carbon fiber-reinforcedcomposites (also referred to as “CFR composites”). When interlayerdelamination occurs, structural integrity of such articles iscompromised, sometimes leaving the composite article useless asintended. Further, in extreme cases where the composite articlefractures, a sharp broken surface can result (i.e., with reinforcingfibers extending haphazardly therefrom), which impacts not only theusefulness of the article, but also the safety of those using sucharticles and those around them. Thus, breakage prevention andcontainment are also important design factors.

In order to enhance certain properties of composite articles, gel coatsor similar protective coatings have conventionally been used. Gel coatsoften impart a glossy appearance and improve other aesthetic propertiesof the article. In addition, gel coats can provide some, althoughlimited, enhancements in abrasion resistance. Gel coats or similarprotective coatings are conventionally applied to composite articlesthat are formed by molding for, if no other reason, aestheticenhancement. Particularly when molding articles from compositematerials, surface imperfections are likely to develop, giving rise to aneed for aesthetic enhancement. One mechanism for the increased numberof surface imperfections in molded composite articles is associated withtiny air bubbles forming at the interface with the mold when the polymermatrix of such composites does not sufficiently flow throughout thereinforcement (e.g., fibers) during molding. The result is that thesurface of the composite article, which is formed against the face ofthe mold, contains imperfections that can detract from a glass-likeappearance otherwise desired.

There are two widely used methods of applying gel coats or similarexterior protective coatings to composite articles. The first methodinvolves spraying the gel coat onto an exterior surface of a compositearticle after the article is formed (e.g., by molding). The secondmethod involves eliminating this subsequent processing (e.g.,post-molding) step by pre-applying the gel coat to the interior surfaceof, for example, a mold where it can then be transferred to an exteriorsurface of the composite article formed therein. For example, see U.S.Pat. Nos. 4,081,578; 4,748,192; and 5,849,168. This method, which is onevariation of “in-mold processing,” is sometimes referred to as in-molddeclaration or in-mold labeling depending on the application andmaterials used. Another variation in the use of in-mold processing forapplication of materials, although complicated and inefficient, isdescribed in U.S. Pat. No. 5,768,285.

While gel coats are capable of improving the aesthetics of surfaces towhich they are applied, they are often not capable of imparting some orall of the desired performance properties. For example, gel coats areoften too thin or too hard to provide substantial levels of abrasionresistance. Further, gel coats typically do not provide significantimpact resistance when used on composite articles. After extended use,gel coats also have a tendency to crack, which enables water topenetrate into articles on which they are applied. Over time, such waterpenetration may lead to significant structural damage of the compositearticle. When the article is subjected to freeze-thaw cycling (e.g., aswith many aerospace parts that undergo several freeze-thaw cycles in asingle day of operation), premature structural failure is often morerapid, as any water trapped within the composite article will likelyproduce larger cracks and similar internal damage based on suchfreeze-thaw cycling.

In addition to their inability to often provide desired performanceproperties, use of gel coats typically decreases overall processingefficiency. For example, if the gel coat is spray-applied to a surfacein a post-processing step, additional labor and manufacturing time isrequired in conjunction therewith. Even when applied in-mold, forexample, typical gel coats require cure time after application to a moldsurface and before actual molding of the composite article. Such curetime can take several hours, which is obviously undesirable from theperspective of processing efficiency.

While in-mold processing is otherwise generally more efficient thanpost-mold application of gel coats, if printed material (e.g., a textualor graphical decal) is applied to the surface of a finished compositearticle, a gel coat must then be conventionally spray-applied to thatsurface or a protective coating or protective sheet must generally beapplied over the printed material as a post-processing step. This isoften necessary even if a gel coat has already been applied to thesurface in-mold.

The types of materials that can be applied as a gel coat are alsolimited, which is undesirable as it decreases flexibility in design andmanufacture of composite articles. For example, many conventional gelcoat materials are two-part compounds having a relatively short potlife, which requires that they be used within a few hours of compoundingor discarded. When in-mold application of gel coats is desired,additional constraints must be considered. For example, availability ofcertain polymer matrix systems for in-mold processing, such as thosebased on epoxy thermoset resins used with carbon fiber reinforcements,is very limited.

It should be noted that materials other than gel coats have been applied“in-mold” and to different types of underlying surfaces. For example,multi-layer paint replacement film has been converted to a finishedproduct through an in-mold decoration process. This process typicallyinvolves back molding of the film to form a finished article having thepaint replacement film integrally adhered to the outer surface. In-moldprocessing has also been utilized to construct certain specializedsporting implements such as bicycle helmets, where a foam layer isin-mold bonded to the hard outer shell of the helmet. Nevertheless,application of exterior protective coverings to surfaces, particularlythose exterior surfaces formed from composite materials, is in need ofimprovement.

To provide higher levels of abrasion resistance or impact resistancebeyond what gel coats alone can provide, protective sheets have beenadded to the exterior surfaces of composite articles in addition to gelcoats. As compared to a protective coating, such as a gel coat, a“protective sheet” is generally applied to a surface in its cured form.In contrast, a coating is generally applied to a surface to be protectedin an uncured (e.g., solution) form, after which it is cured in-situ.While a sheet may be formed using conventional extrusion, casting, orcoating technology, before the sheet is applied to a surface to beprotected it is cured and/or formed.

Conventional protective sheets are often applied to a surface using apressure sensitive adhesive. Many undesirable issues can arise, however,if the pressure sensitive adhesive is not adequately designed andformulated. For example, many pressure sensitive adhesives lack adequatebond strength to prevent edge lifting of protective sheets that areadhered to an underlying surface using the same. Protective sheetsapplied using existing technologies are typically not permanently bondedto the underlying surface. The durability of such constructions is oftenshort-lived, as the adhesive bond often fails during repeated use,causing the protective sheet to lift from the surface. As anotherexample, many conventional pressure sensitive adhesives are eitherrepositionable and/or removable. This allows conventional protectivesheets, which may lack adequate extensibility for easy application to asurface (especially irregular-shaped surfaces), to be more easilyapplied to surfaces. However, such pressure sensitive adhesivestypically lack adequate permanency. In addition, often when a pressuresensitive adhesive is used for bonding a protective sheet to anunderlying surface, a gel coat or other protective coating is often usedin addition to the protective sheet (e.g., a coating is applied to anunderlying surface before the protective sheet is applied).

In addition to the shortcomings associated with bonding of protectivesheets to an underlying surface, application of protective sheets hasproven to be otherwise difficult. For example, in addition to thebonding issues arising based on the often inadequately extensible natureof conventional protective sheets, it is often difficult to applyprotective sheets to surfaces with complex shapes when relatively thickor multi-layer protective sheets are used. As a result, wrinkles oftenexist in protective sheets so applied. Even if uniformly applied toirregular surfaces initially, over time conventional protective sheetsare prone to lifting from such surfaces. In any event, the way in whichprotective sheets are typically applied to such surfaces generallydecreases processing efficiency.

While some benefits can be obtained from application of protectivesheets and protective coatings according to known methods, suchconventional methods often result in composite articles that still failto adequately address important performance and processingconsiderations. Not only are performance property considerationsimportant, but for the reasons stated above, aesthetics are also oftenanother important consideration.

When attempting to address the myriad of important considerations,however, processing efficiency is often compromised. This is the casewhen, for example, multiple protective sheets and/or protective coatings(e.g., gel coats) are applied to a surface. In order to improveprocessing efficiency, it is desirable to minimize the number ofprotective sheets and protective coatings such as gel coats (especiallythose gel coats used primarily for aesthetic enhancement) that areapplied to protect surfaces of underlying composite articles. Forexample, if gel coats could be eliminated, processing efficiency couldimprove both in terms of cost and time savings associated with theotherwise required additional processing steps associated with gelcoating.

BRIEF SUMMARY OF THE INVENTION

A wide variety of composite articles benefit from application ofprotective sheets according to the invention. Composite articles of theinvention are useful in a range of indoor and outdoor applications—forexample, the transportation, architectural and sporting goodsindustries. In certain embodiments of the invention, the compositearticle comprises at least a portion of a motorized vehicle, at least aportion of an aerospace component, or at least a portion of a sportingimplement (e.g., a shaft-based sporting implement). For example, thecomposite article can comprise at least a portion of a golf club, abicycle frame, a hockey stick, a lacrosse stick, a ski pole, a ski, afishing rod, a tennis racket, an arrow, a polo mallet, or a bat.

According to one aspect of the invention, a composite article comprisesa protective sheet integrally bonded to at least one portion thereof.According to another aspect of the invention, a composite articlecomprises an exterior protective sheet adhered to an underlyingcomposite material surface, wherein the composite article is essentiallyfree of additional layers between the protective sheet and theunderlying composite material surface. According to yet another aspectof the invention, a composite article comprises a protective sheetadhered to at least one exterior portion thereof, wherein the protectivesheet is capable of providing all desired enhancements in performanceand aesthetic properties of the composite article in one protectivesheet component as compared to use of multiple protective sheet orprotective coating components.

In some embodiments, the composite article comprises printed material onat least one outwardly visible surface thereof. In some embodiments, thecomposite material comprises a fiber-reinforced composite. In anexemplary embodiment, at least a portion of the protective sheet iscrosslinked with at least a portion of the composite article.

In one embodiment, the composite article has at least one exteriorsurface comprising a composite material and the protective sheet fullycovers that exterior surface. In another embodiment, the compositearticle is fully covered by the protective sheet.

Any suitable materials can be used to form the composite article. Thecomposite article can be based on a thermoplastic resin or a thermosetresin (e.g., an epoxy resin, such as Bisphenol-A or Bisphenol-F epoxy)in combination with a reinforcing material. In an exemplary embodiment,the composite article comprises a fiber-reinforced composite materialunderlying the protective sheet.

Similarly, any suitable materials can be used for the protective sheetand to form the same. Preferably, the protective sheet is extensible. Inan exemplary embodiment, the protective sheet comprises at least oneelastomeric material (e.g., an elastomeric material based onpolyurethane, ionomer, or fluoroelastomer chemistry).

In one embodiment, the protective sheet comprises at least onepolyurethane-based layer. For example, the polyurethane-based layer cancomprise at least one aliphatic-based polyurethane, such as thoseselected from polyether-based aliphatic polyurethanes, polyester-basedaliphatic polyurethanes, polycaprolactone-based aliphatic polyurethanes,and polycarbonate-based aliphatic polyurethanes. In a furtherembodiment, the composite article is based on at least one epoxy resinand the protective sheet comprises at least one polyurethane-basedlayer.

Methods of the invention include those for applying protective sheets ofthe invention to composite articles. According to these methods, aprotective sheet is applied to at least a portion of an exterior surfaceformed from a composite material and where protection is desired.According to one embodiment of a method of the invention, at least oneexterior surface of the composite article to be protected is integrallyformed in the presence of the protective sheet.

For example, a method of applying a protective sheet to at least aportion of an exterior surface of a composite article comprisesproviding the protective sheet prior to forming the exterior surface ofthe composite article and integrally forming the exterior surface of thecomposite article in the presence of the protective sheet such that atleast a portion of the exterior surface of the composite article and theprotective sheet become integrally bonded. In order to promotecrosslinking between the composite article and the protective sheet, theprotective sheet can undergo thermolysis during cure of the compositearticle according to one aspect of the invention and depending onmaterials used for the various components.

In one embodiment, the exterior surface of the composite article isformed using an in-mold processing or insert-mold processing technique,such as a vacuum bag processing technique. In an exemplary embodiment,the exterior surface of the composite article comprises afiber-reinforced composite material prior to application of theprotective sheet to at least a portion thereof.

Another method of the invention comprises applying a protective sheet toat least a portion of an exterior surface of a composite article. Themethod comprises providing the protective sheet, forming the exteriorsurface of the composite article, and co-molding the protective sheet tothe exterior surface of the composite article such that at least aportion of the exterior surface of the composite article and theprotective sheet become integrally bonded. In one embodiment, theexterior surface of the composite article comprises a fiber-reinforcedcomposite material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional representation of an exemplary vacuum bagprocessing configuration for application of protective sheets of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed toward improved composite articlescomprising a protective sheet on at least a portion of at least oneexterior surface thereof. “Composite articles” of the invention arethose articles comprising at least one composite material.

Composite articles are formed based on at least one matrix material andat least one reinforcing material. The combination of a matrix material(e.g., resin) and a reinforcing material (e.g., fibers) within acomposite material often produces extremely strong articles that arealso lightweight.

Exemplary matrix materials include epoxy resins, ester resins (e.g.,vinyl esters), phenolic resins, bismaleimide resins, polyimide resinsand other thermosetting resins. Epoxy resins tend to be the most common.The matrix material can also be a thermoplastic resin.

While a composite material can contain any suitable reinforcementmaterial, fibrous reinforcement is common. Such reinforcement can becontinuous or discrete. Exemplary forms of continuous fiberreinforcement include those containing woven, nonwoven, mat, braided,random, uni-directional, or other forms of continuous fibers. Typicalfibrous reinforcement materials include carbon fibers, glass fibers,aramid fibers, boron fibers, polyethylene fibers, and others.

While a sheet material may be used primarily for aesthetic purposes incertain applications, such a purpose or use does not exclude such sheetsfrom being encompassed within the definition of protective sheetsreferenced throughout in describing the present invention. Among otherbeneficial properties, the presence of the protective sheet enhancesdurability (e.g., abrasion resistance) of the composite article, as wellas its impact resistance and fracture toughness in further embodiments.

In addition to enhanced performance properties associated with compositearticles of the invention, processing efficiency is increased ascompared to conventional articles and methods. According to exemplaryembodiments, protective coatings (e.g., gel coats or similar protectivecoatings) are not needed to obtain desired properties and, thus, can beeliminated from composite articles of the invention. Such additional orinferior protective coatings are capable of being eliminated asaesthetic enhancement is typically not necessary in composite articlesmade according to the invention. As such, even if conventional gel coatsare used within composite articles of the invention, aesthetics of thecomposite article would typically be essentially the same as those ofcomparable articles without the gel coat.

In essence, protective sheets of the invention and methods of theirapplication are capable of providing all desired performance andaesthetic properties in one component and without requiring use ofmultiple protective sheets and/or multiple protective coatings in orderto obtain comparable properties. By eliminating undesirable protectivecoatings and multiple protective layers, additional processing stepsassociated with conventional methods for protection of compositesurfaces are likewise eliminated. Similarly, additional processing timeassociated therewith, such as when a gel coat is applied in-mold in away that requires cure time after application to a mold surface andbefore actual molding of the composite article, is also eliminated.

Even when printed material is included on an exterior surface of acomposite article, addition of a protective coating after applicationthereof to the surface is not required according to an exemplaryembodiment of the invention. According to this embodiment, any printedmaterial desired to be placed on an exterior surface of a compositearticle is pre-printed onto a protective sheet prior to its bonding tothe underlying composite article. The protective sheet is then appliedto the surface of an underlying composite article such that the printedmaterial is outwardly visible.

Composite articles comprising protective sheets according to theinvention are useful in a range of indoor and outdoor applications—forexample, the transportation, architectural and sporting goodsindustries. An exemplary embodiment of the invention relates tocomposite articles used in the automotive industry. Such articlesinclude, for example, interior trim components (e.g., door handles,steering wheels, and gear shift knobs), internal mechanical components(e.g., drive shaft components), and exterior components (e.g., doorpanels, other body panels, roofs, fenders, hoods, and bumpers).

An exemplary embodiment of the invention relates to shaft-based sportingimplements and similar articles. Such articles include, for example,golf clubs, bicycle frames, hockey sticks, lacrosse sticks, skis, skipoles, fishing rods, tennis rackets, arrows, polo mallets, and bats.According to a preferred aspect of this embodiment, the portion of thesurface where the protective sheet is applied is not the primary surfacefor impact by a ball, puck, or other object (i.e., the surface is notwhat may be commonly referred to as the “contact surface”). For example,when the composite article is a hockey stick, the protective sheet ispreferably applied to the shaft as opposed to the blade. Similarly, whenthe composite article is a golf club, the protective sheet is preferablyapplied to the shaft as opposed to the club head. Likewise, when thecomposite article is a lacrosse stick, the protective sheet ispreferably applied to the handle as opposed to the pocket. When thecomposite article is a baseball bat, the protective sheet is preferablyapplied to the handle as opposed to the barrel.

In certain applications, the presence of the protective sheet can meanthe difference between having a usable piece of sporting equipmentand/or one that is safe. For example, when a cross country skier's polebreaks during a race they must either forfeit the race or be luckyenough to be given another pole to use. As a further example, it is notuncommon to break several hockey sticks during a game. Each timeconventional technology is used, the hockey stick has the potential toseverely injure another person or the player as its shape can readilytransform into that of a spear-like object when broken. By usingcomposite articles of the present invention, the equipment may still beusable (e.g., as in the case of the cross country ski pole) or at leastresist total failure for a longer period of time. In addition, whencomposite articles of the present invention are used, the equipment maybe prevented from injuring somebody upon failure (e.g., as in the caseof a splintered hockey stick).

In certain embodiments, advantages of the invention are maximized whenthe protective sheet is applied to substantially cover the entireunderlying surface. That is, the protective sheet fully covers theunderlying composite material. In comparison, partial coverage of anunderlying composite material may not adequately contain or preventbreakage of the overall composite article in those applications. Thus,in an exemplary embodiment, the protective sheet is applied to fullycover the underlying composite material within a composite article. In afurther embodiment, the protective sheet is applied to fully cover theoverall underlying composite article or an individual component thereof.

Advantages of the invention are more fully realized when the surface towhich the protective sheet is applied is rigid, as is the case with mostcomposite materials. “Rigid” refers to those surfaces that areinflexible in that they do not easily bend or substantially change shapewhen pressure is applied thereto. Rigidity is often imparted when usingfiber-reinforced composite materials. Thus, in an exemplary embodiment,the composite article to which the protective sheet is applied comprisesa fiber-reinforced composite material. As known to those skilled in theart, a wide variety of materials can be used as the fibrousreinforcement. In sporting implements, however, carbon fibers are thepredominantly used fibrous reinforcement.

In a further embodiment, the composite article comprises at least oneprotective sheet integrally bonded to an underlying surface. Accordingto this embodiment, performance benefits from the presence of theprotective sheet are further enhanced and more reliable than when theprotective sheet is not integrally bonded as such. “Integrally bonded”refers to those materials with bonds formed between the protective sheetand underlying composite article that are essentially permanent innature. Removal of an integrally bonded protective sheet typicallyrequires more force than that required to separate the same protectivesheet adhered using certain pressure sensitive adhesives (e.g., thosepressure sensitive adhesives having low shear and low tack,removability, repositionability, or similar properties) that do notfacilitate formation of permanent or durable bonds. Integrally bondedprotective sheets are better able to contain underlying compositematerials than conventionally adhered protective sheets due to thereduced chances that their bonds to underlying surfaces will fail.

According to the invention, at least one protective sheet is integrallybonded to at least a portion of at least one surface of an underlyingcomposite article. Protective sheets of the invention are formed usingany suitable method. In one embodiment, the protective sheet isgenerally planar. In exemplary embodiments, however, protective sheetsare also pre-formed into a shape approximating the shape of the surfaceonto which it is to be adhered. This simplifies the process ofadequately adhering the protective sheet to the surface and can be done,for example, by thermoforming or injection molding. Whatever the methodused for its fabrication, the protective sheet is formed separately fromformation of the exterior surface of the composite article to which itwill be applied. Thus, for example, protective sheets of the inventiondo not require, and generally do not include, protective coatings formedby spray coating a surface of a composite article with a compositionthat forms a protective layer on the surface.

The protective sheet can be any suitable thickness. In one embodiment,protective sheets of the invention are about 50 μm (0.002 inch) to about1.1 mm (0.045 inch) thick at their maximum thickness. In a furtherembodiment, protective sheets of the invention are about 80 μm (0.003inch) to about 0.64 mm (0.025 inch) thick at their maximum thickness. Instill further embodiments, protective sheets of the invention are about0.15 mm (6 mils) to about 0.38 mm (15 mils) thick at their maximumthickness.

The protective sheet can be any suitable material and may include one ormore layers. Protective sheets of the invention comprise at least a baselayer and, optionally, topcoat or other layers. The use of multiplelayers within a protective sheet imparts flexibility in design ofprotective sheets. While there may be protective sheets that do notinvolve multiple layers, but rather one layer, certain performanceproperties can often be better achieved when using a protective sheetcomprising multiple layers.

In an exemplary embodiment, the protective sheet comprises one or moreelastomeric materials. Elastomeric materials are preferably thosepolymeric materials exhibiting about 200% or greater elastic elongation.Elastomeric materials are preferred for use in the protective sheets ofthe invention because such materials are highly resilient and exhibitcompressive recovery. Thus, elastomeric materials can enhance impactresistance, abrasion resistance, and other similar performanceproperties of surfaces and articles to which protective sheetscomprising the same are applied. Further, elastomeric materials aregenerally highly extensible and conformable. Thus, when used inprotective sheets of the invention, such materials ease application ofsuch protective sheets to articles or molds of varying dimensions andshape. Exemplary elastomeric films include those based on polyurethane,ionomer, and fluoroelastomer chemistries. Extensible protective sheetsare formed according to one aspect of this embodiment.

The terms “extensible” and “extensibility” refer to a material'sductility and its ability to be stretched and recover to essentially itsoriginal state after stretching. Extensible protective sheets arecapable of recovering to their original state when stretched (i.e.,elongated) up to about 125% of their initial length or more. Preferably,extensible protective sheets are capable of recovering to their originalstate when stretched up to about 150% of their initial length or more.According to one aspect of the invention, extensible protective sheetsare capable of elongating more than 200% before breaking. Furtherpreferable are extensible protective sheets that exhibit essentially noplastic deformation when stretched up to about 150% of their initiallength.

According to one aspect of the invention, extensible protective sheetsof the invention exhibit greater than about 210% elongation at breakwhen tested according to the Tensile Testing Method described below. Ina further embodiment, extensible protective sheets of the inventionexhibit greater than about 260% elongation at break when testedaccording to the Tensile Testing Method described below. In a stillfurther embodiment, extensible protective sheets of the inventionexhibit greater than about 300% elongation at break when testedaccording to the Tensile Testing Method described below. In a furtherembodiment still, extensible protective sheets of the invention exhibitgreater than about 350% elongation at break when tested according to theTensile Testing Method described below.

According to another aspect of the invention, extensible protectivesheets of the invention exhibit less than about 3% deformation after 25%elongation when tested according to the Recovery Testing Methoddescribed below. In a further embodiment, extensible protective sheetsof the invention exhibit less than about 2% deformation after 25%elongation when tested according to the Recovery Testing Methoddescribed below. In a still further embodiment, extensible protectivesheets of the invention exhibit less than about 1% deformation after 25%elongation when tested according to the Recovery Testing Methoddescribed below.

According to another aspect of the invention, extensible protectivesheets of the invention exhibit less than about 8% deformation after 50%elongation when tested according to the Recovery Testing Methoddescribed below. In a further embodiment, extensible protective sheetsof the invention exhibit less than about 5% deformation after 50%elongation when tested according to the Recovery Testing Methoddescribed below. In a still further embodiment, extensible protectivesheets of the invention exhibit less than about 2% deformation after 50%elongation when tested according to the Recovery Testing Methoddescribed below.

According to another aspect of the invention, extensible protectivesheets of the invention require a force of less than about 40 Newtons toelongate the sheet to 150% its initial length. In a further embodiment,extensible protective sheets of the invention require a force of lessthan about 30 Newtons to elongate the sheet to 150% its initial length.In yet a further embodiment, extensible protective sheets of theinvention require a force of less than about 20 Newtons to elongate thesheet to 150% its initial length.

In an exemplary embodiment, protective sheets of the invention arepolyurethane-based in that they comprise at least one polyurethane-basedlayer. For simplicity, the term “polyurethane” as used herein includespolymers containing urethane (also known as carbamate) linkages, urealinkages, or combinations thereof (i.e., in the case ofpoly(urethane-urea)s). Thus, polyurethanes of the invention contain atleast urethane linkages and, optionally, urea linkages. In oneembodiment, polyurethane-based layers of the invention are based onpolyurethanes where the backbone has at least about 80% urethane and/orurea repeat linkages formed during their polymerization.

Polyurethane chemistry is well known to those of ordinary skill in theart. Polyurethane-based layers of the invention can contain polyurethanepolymers of the same or different chemistries, the latter commonlyunderstood to be a polymer blend. Polyurethanes generally comprise thereaction product of at least one isocyanate-reactive component, at leastone isocyanate-functional component, and one or more other optionalcomponents such as emulsifiers and chain extending agents.

Components of polyurethanes are further described below, with referenceto certain terms understood by those in the chemical arts as referringto certain hydrocarbon groups. Reference is also made throughout topolymeric versions thereof. In that case, the prefix “poly” is insertedin front of the name of the corresponding hydrocarbon group. Exceptwhere otherwise noted, such hydrocarbon groups, as used herein, mayinclude one or more heteroatoms (e.g., oxygen, nitrogen, sulfur, orhalogen atoms), as well as functional groups (e.g., oxime, ester,carbonate, amide, ether, urethane, urea, carbonyl groups, or mixturesthereof).

The term “aliphatic group” means a saturated or unsaturated, linear,branched, or cyclic hydrocarbon group. This term is used to encompassalkylene (e.g., oxyalkylene), aralkylene, and cycloalkylene groups, forexample.

The term “alkylene group” means a saturated, linear or branched,divalent hydrocarbon group. Particularly preferred alkylene groups areoxyalkylene groups. The term “oxyalkylene group” means a saturated,linear or branched, divalent hydrocarbon group with a terminal oxygenatom. The term “aralkylene group” means a saturated, linear or branched,divalent hydrocarbon group containing at least one aromatic group. Theterm “cycloalkylene group” means a saturated, linear or branched,divalent hydrocarbon group containing at least one cyclic group. Theterm “oxycycloalkylene group” means a saturated, linear or branched,divalent hydrocarbon group containing at least one cyclic group and aterminal oxygen atom. The term “aromatic group” means a mononucleararomatic hydrocarbon group or polynuclear aromatic hydrocarbon group.The term includes arylene groups. The term “arylene group” means adivalent aromatic group.

Any suitable method can be used for preparation of polyurethanes for usein polyurethane-based protective sheets of the invention. In oneembodiment, the polyurethane is prepared and formed into a single layerusing an extruder. The polyurethane can also be blown to form a singlelayer.

Many commercially available polyurethanes are available and suitable foruse in preparing protective sheets of the invention. Extrusion gradepolyurethanes can be used in certain embodiments of the invention.Extrusion grade polyurethanes include those available from StevensUrethane of Easthampton, Mass. Aliphatic polyurethanes from StevensUrethane, for example, those designated SS-1219-92 and SS-2219-92.Suitable polyurethanes are also available from Thermedics (Noveon, Inc.)of Wilmington, Mass., under the TECOFLEX trade designation (e.g.,CLA-93AV) and from Bayer MaterialScience LLC of Pittsburgh, Pa., underthe TEXIN trade designation (e.g., aliphatic ester-based polyurethanesuitable as a base polymer for polyurethane-based layers of theinvention is available under the trade designation, TEXIN DP7-3008).Polycaprolactone-based aliphatic polyurethane is available from Argotec,Inc. of Greenfield, Mass. under the trade designation, ARGOTEC 49510.Polyether-based aliphatic thermoplastic polyurethane is available fromArgotec, Inc. of Greenfield, Mass. under the trade designations, ARGOTECPE-399 and ARGOTEC PE-192. Similar polyurethanes are available fromStephens Urethane of Easthampton, Mass., under the trade designations,AG8451 and AG8320. Still further, similar polyurethanes are availablefrom Deerfield Urethane, Inc. of Whately, Mass. (a Bayer MaterialSciencecompany) under the trade designations Deerfield Urethane A4700 andDeerfield Urethane A4100. Polyester-based aliphatic polyurethanes arealso suitable for use in the invention. Polycarbonate-basedpolyurethanes, such as those described in U.S. Pat. No. 4,476,293 arelikewise suitable for use in the invention. In addition, U.S. Pat. Nos.5,077,373 and 6,518,389 describe further suitable polyurethanes.

In another embodiment, polyurethane can be prepared and formed into asingle layer using solution or dispersion chemistry and coatingtechniques known to those skilled in the art. Such a layer can beprepared by reacting components, including at least oneisocyanate-reactive component, at least one isocyanate-functionalcomponent, and, optionally, at least one reactive emulsifying compound,to form an isocyanate-terminated polyurethane prepolymer. Thepolyurethane prepolymer can then be dispersed, and optionallychain-extended, in a dispersing medium to form a polyurethane-baseddispersion that can be cast to form a layer of polyurethane. Whenpolyurethane is prepared from an organic solventborne or waterbornesystem, once the solution or dispersion is formed, it is easily appliedto a substrate and then dried to form a polyurethane layer. As known tothose of ordinary skill in the art, drying can be carried out either atroom temperature (i.e., about 20° C.) or at elevated temperatures (e.g.,about 25° C. to about 150° C.). For example, drying can optionallyinclude using forced air or a vacuum. This includes the drying ofstatic-coated substrates in ovens, such as forced air and vacuum ovens,or drying of coated substrates that are continuously conveyed throughchambers heated by forced air, high-intensity lamps, and the like.Drying may also be performed at reduced (i.e., less than ambient)pressure.

Any suitable isocyanate-reactive component can be used in thisembodiment of the present invention. The isocyanate-reactive componentcontains at least one isocyanate-reactive material or mixtures thereof.As understood by one of ordinary skill in the art, anisocyanate-reactive material includes at least one active hydrogen.Those of ordinary skill in the polyurethane chemistry art willunderstand that a wide variety of materials are suitable for thiscomponent. For example, amines, thiols, and polyols areisocyanate-reactive materials.

It is preferred that the isocyanate-reactive material be ahydroxy-functional material. Polyols are the preferredhydroxy-functional material used in the present invention. Polyolsprovide urethane linkages when reacted with an isocyanate-functionalcomponent, such as a polyisocyanate.

Polyols, as opposed to monols, have at least two hydroxy-functionalgroups. Diols contribute to formation of relatively high molecularweight polymers without requiring crosslinking, such as isconventionally introduced by polyols having greater than twohydroxy-functional groups. Examples of polyols useful in the presentinvention include, but are not limited to, polyester polyols (e.g.,lactone polyols) and the alkylene oxide (e.g., ethylene oxide;1,2-epoxypropane; 1,2-epoxybutane; 2,3-epoxybutane; isobutylene oxide;and epichlorohydrin) adducts thereof, polyether polyols (e.g.,polyoxyalkylene polyols, such as polypropylene oxide polyols,polyethylene oxide polyols, polypropylene oxide polyethylene oxidecopolymer polyols, and polyoxytetramethylene polyols;polyoxycycloalkylene polyols; polythioethers; and alkylene oxide adductsthereof), polyalkylene polyols, polycarbonate polyols, mixtures thereof,and copolymers therefrom.

Polycarbonate-based polyurethanes are preferred according to oneembodiment. It was found that this type of polyurethane chemistry easilyfacilitated obtainment of polyurethane-based protective sheets withproperties desired. See U.S. Pat. No. 4,476,293 for a description ofexemplary polycarbonate-based polyurethanes.

In one preferred embodiment, a polycarbonate diol is used to preparepolycarbonate-based polyurethane according to the invention. Althoughpolyols containing more than two hydroxy-functional groups are generallyless preferred than diols, certain higher functional polyols may also beused in the present invention. These higher functional polyols may beused alone, or in combination with other isocyanate-reactive materials,for the isocyanate-reactive component.

For broader formulation latitude, at least two isocyanate-reactivematerials, such as polyols, may be used for the isocyanate-reactivecomponent. However, as any suitable isocyanate-reactive component can beused to form the polyurethane, much latitude is provided in the overallpolyurethane chemistry.

The isocyanate-reactive component is reacted with anisocyanate-functional component during formation of the polyurethane.The isocyanate-functional component may contain oneisocyanate-functional material or mixtures thereof. Polyisocyanates,including derivatives thereof (e.g., ureas, biurets, allophanates,dimers and trimers of polyisocyanates, and mixtures thereof),(hereinafter collectively referred to as “polyisocyanates”) are thepreferred isocyanate-functional materials for the isocyanate-functionalcomponent. Polyisocyanates have at least two isocyanate-functionalgroups and provide urethane linkages when reacted with the preferredhydroxy-functional isocyanate-reactive components. In one embodiment,polyisocyanates useful for preparing polyurethanes are one or acombination of any of the aliphatic or aromatic polyisocyanates commonlyused to prepare polyurethanes.

Generally, diisocyanates are the preferred polyisocyanates. Usefuldiisocyanates include, but are not limited to, aromatic diisocyanates,aromatic-aliphatic diisocyanates, aliphatic diisocyanates,cycloaliphatic diisocyanates, and other compounds terminated by twoisocyanate-functional groups (e.g., the diurethane oftoluene-2,4-diisocyanate-terminated polypropylene oxide polyol).

Examples of preferred diisocyanates include the following: 2,6-toluenediisocyanate; 2,5-toluene diisocyanate; 2,4-toluene diisocyanate;phenylene diisocyanate; 5-chloro-2,4-toluene diisocyanate;1-chloromethyl-2,4-diisocyanato benzene; xylylene diisocyanate;tetramethyl-xylylene diisocyanate; 1,4-diisocyanatobutane;1,6-diisocyanatohexane; 1,12-diisocyanatododecane;2-methyl-1,5-diisocyanatopentane;methylenedicyclohexylene-4,4′-diisocyanate;3-isocyanatomethyl-3,5,5′-trimethylcyclohexyl isocyanate (isophoronediisocyanate); 2,2,4-trimethylhexyl diisocyanate;cyclohexylene-1,4-diisocyanate; hexamethylene-1,6-diisocyanate;tetramethylene-1,4-diisocyanate; cyclohexane-1,4-diisocyanate;naphthalene-1,5-diisocyanate; diphenylmethane-4,4′-diisocyanate;hexahydro xylylene diisocyanate; 1,4-benzene diisocyanate;3,3′-dimethoxy-4,4′-diphenyl diisocyanate; phenylene diisocyanate;isophorone diisocyanate; polymethylene polyphenyl isocyanate;4,4′-biphenylene diisocyanate;4-isocyanatocyclohexyl-4′-isocyanatophenyl methane; andp-isocyanatomethyl phenyl isocyanate.

When preparing polyurethane dispersions for casting into layers ofpolyurethane, the isocyanate-reactive and isocyanate-functionalcomponents may optionally be reacted with at least one reactiveemulsifying compound according to one embodiment of the invention. Thereactive emulsifying compound contains at least one anionic-functionalgroup, cationic-functional group, group that is capable of forming ananionic-functional group or cationic-functional group, or mixturesthereof. This compound acts as an internal emulsifier because itcontains at least one ionizable group. Thus, these compounds aregenerally referred to as “reactive emulsifying compounds.”

Reactive emulsifying compounds are capable of reacting with at least oneof the isocyanate-reactive and isocyanate-functional components tobecome incorporated into the polyurethane. Thus, the reactiveemulsifying compound contains at least one, preferably at least two,isocyanate- or active hydrogen-reactive- (e.g., hydroxy-reactive)groups. Isocyanate- and hydroxy-reactive groups include, for example,isocyanate, hydroxyl, mercapto, and amine groups.

Preferably, the reactive emulsifying compound contains at least oneanionic-functional group or group that is capable of forming such agroup (i.e., an anion-forming group) when reacted with theisocyanate-reactive (e.g., polyol) and isocyanate-functional (e.g.,polyisocyanate) components. The anionic-functional or anion-forminggroups of the reactive emulsifying compound can be any suitable groupsthat contribute to ionization of the reactive emulsifying compound. Forexample, suitable groups include carboxylate, sulfate, sulfonate,phosphate, and similar groups. As an example, dimethylolpropionic acid(DMPA) is a useful reactive emulsifying compound. Furthermore,2,2-dimethylolbutyric acid, dihydroxymaleic acid, and sulfopolyesterdiol are other useful reactive emulsifying compounds. Those of ordinaryskill in the art will recognize that a wide variety of reactiveemulsifying compounds are useful in preparing polyurethanes for thepresent invention.

One or more chain extenders can also be used in preparing polyurethanesof the invention. For example, such chain extenders can be any or acombination of the aliphatic polyols, aliphatic polyamines, or aromaticpolyamines conventionally used to prepare polyurethanes.

Illustrative of aliphatic polyols useful as chain extenders include thefollowing: 1,4-butanediol; ethylene glycol; 1,6-hexanediol; glycerine;trimethylolpropane; pentaerythritol; 1,4-cyclohexane dimethanol; andphenyl diethanolamine. Also note that diols such as hydroquinonebis(β-hydroxyethyl)ether;tetrachlorohydroquinone-1,4-bis(β-hydroxyethyl)ether; andtetrachlorohydroquinone-1,4-bis(β-hydroxyethyl)sulfide, even though theycontain aromatic rings, are considered to be aliphatic polyols forpurposes of the invention. Aliphatic diols of 2-10 carbon atoms arepreferred. Especially preferred is 1,4-butanediol.

Illustrative of useful polyamines are one or a combination of thefollowing: p,p′-methylene dianiline and complexes thereof with alkalimetal chlorides, bromides, iodides, nitrites and nitrates;4,4′-methylene bis(2-chloroaniline); dichlorobenzidine; piperazine;2-methylpiperazine; oxydianiline; hydrazine; ethylenediamine;hexamethylenediamine; xylylenediamine; bis(p-aminocyclohexyl)methane;dimethyl ester of 4,4′-methylenedianthranilic acid; p-phenylenediamine;m-phenylenediamine; 4,4′-methylene bis(2-methoxyaniline); 4,4′-methylenebis(N-methylaniline); 2,4-toluenediamine; 2,6-toluenediamine; benzidine;3,4′-dimethylbenzidine; 3,3′-dimethoxybenzidine; dianisidine;1,3-propanediol bis(p-aminobenzoate); isophorone diamine;1,2-bis(2′-aminophenylthio)ethane; 3,5-diethyl toluene-2,4-diamine; and3,5-diethyl toluene-2,6-diamine. The amines preferred for use are4,4′-methylene bis(2-chloroaniline); 1,3-propanediolbis(p-aminobenzoate); and p,p′-methylenedianiline and complexes thereofwith alkali metal chlorides, bromides, iodides, nitrites and nitrates.

Any suitable additives can be present in protective sheets of theinvention. Many different types of additives can be used and are readilyavailable. For example, stabilizers, antioxidants, plasticizers,tackifiers, adhesion promoters (e.g., silanes, glycidyl methacrylate,and titanates), lubricants, colorants, pigments, dyes, polymericadditives (e.g., polyacetals, reinforcing copolymers, andpolycaprolactone diols), and the like can be used in certain embodimentsof the invention. In certain embodiments, however, use of additivesdetracting from optical clarity of the protective sheet are minimized oreliminated. Such additives include, for example, fiber- or othermatrix-reinforcements typically present in composite materials. Thus, inthis exemplary embodiment, the protective sheet itself would not beconsidered to be a composite material according to those skilled in theart.

According to another embodiment, polyurethane-based protective sheets ofthe invention comprise multiple layers (e.g., a carrier and a topcoat),at least one of which is polyurethane-based. According to one variationof this embodiment, the carrier and the topcoat layers are bothpolyurethane-based. In such an embodiment, the carrier preferablycomprises a polyurethane-based layer as discussed above with respect toa single layer protective sheet of the invention. According to anothervariation of this embodiment, polyurethane-based protective sheets ofthe invention comprise a polyurethane-based topcoat and a carrier layerthat may or may not be polyurethane-based.

When forming a protective sheet comprising a topcoat layer, the topcoatcan be formed using any suitable method. In addition, the topcoat can becrosslinked or uncrosslinked. An uncrosslinked topcoat can be preparedfrom polyurethane-based layers discussed above. If crosslinking isdesired, any suitable method can be used for the same. An exemplarydiscussion of crosslinked topcoats can be found in U.S. Pat. No.6,383,644 and corresponding European Patent No. 1 004 608.

When applying the protective sheet to a composite article, particularlyin applications where composite articles and respective processingequipment have irregular-shaped surfaces, extensibility of theprotective sheet is important. Protective sheets described in co-pendingU.S. provisional patent application No. 60/728,987, filed on Oct. 21,2005, and entitled “Protective Sheets, Articles, and Methods,”incorporated herein by reference in its entirety, were found to besignificantly more extensible than certain commercially availableprotective sheets having a crosslinked topcoat. Accordingly, in afurther embodiment, protective sheets of the invention comprise anessentially uncrosslinked topcoat. In many applications where protectivesheets are used, the potential benefits imparted by crosslinking anexterior layer were substantially outweighed by the significantlyimproved extensibility provided by protective sheets without acrosslinked exterior layer.

Use of extensible protective sheets according to an exemplary embodimentof the invention imparts significant advantages, particularly whenapplying the protective sheet to irregular-shaped surfaces. Further, useof extensible protective sheets in this manner better allows for fullcoverage of the composite article's outer surface with the protectivesheet in certain embodiments of the invention. As noted above, fullcoverage can be beneficial for many applications in enhancingcontainment of the underlying composite material so as to increasesafety and durability when using the composite article.

Several exemplary protective sheets applicable for use according to theinvention are readily available on the market today and can be appliedto the composite article without the additional use of a gel coat orsimilar protective coating. For example, Minnesota Mining &Manufacturing Co. (“3M”) in St. Paul, Minn., markets polyurethane-basedsheet “Paint Protection Film” under the SCOTCHGARD product line. Seealso U.S. Pat. No. 6,383,644. As another example, Venture Tape Corp. inRockland, Mass., markets such sheets (e.g., designated by productnumbers 7510, 7512, and 7514) using the VENTURESHIELD trade designation.Avery Dennison in Strongsville, Ohio markets polyurethane products usingthe STONESHIELD trade designation. Protective sheets are available fromentrotech, inc. of Columbus, Ohio under the ENTROFILM trade designations(e.g., entrofilm 843 and entrofilm 861) and others described inco-pending U.S. Provisional Patent Application No. 60/728,987, filed onOct. 21, 2005, and entitled “Protective Sheets, Articles, and Methods.”

According to the invention, a protective sheet is bonded to anunderlying composite article using any suitable method. For example, theprotective sheet can be adhered to an underlying composite article usingan indirect bonding method. When indirectly bonded, the protective sheetis adhered to the underlying composite article using one or moreadditional layers therebetween. As another example, the protective sheetcan be directly bonded to the exterior surface of a composite article.When directly bonded, the protective sheet is adhered to the underlyingcomposite article without the use of any additional layers (e.g.,adhesives, intermediate coatings, or tie layers) therebetween. Whilesome of the methods described hereinbelow were found useful forintegrally bonding protective sheets to surfaces other than those of acomposite article, the methods are particularly well-suited for formingimproved composite articles of the present invention.

One indirect bonding method involves the application of adhesives,intermediate coatings, or tie layers between the protective sheet andthe underlying composite article. When adhesives are used, they arepreferably selected to form essentially permanent bonds between theprotective sheet and underlying composite article. Thus, thermosetadhesives (e.g., epoxy adhesives) are one candidate for that embodiment.Adequately formulated pressure sensitive adhesives can also be used inother embodiments.

For maximized process efficiency, direct bonding methods are preferred.One direct bonding method involves contacting the protective sheet withand then crosslinking the protective sheet with the matrix material ofthe underlying composite article. Crosslinks are typically relativelystrong covalent bonds between the protective sheet and the underlyingcomposite article. For example, as the matrix material of an underlyingcomposite article cures (e.g., when a matrix material comprises athermoset material), crosslinks form between the surface being cured andthe surface of the protective sheet in contact therewith.

In an exemplary embodiment, the matrix material comprises a thermosetepoxy resin (e.g., Bisphenol-A and/or Bisphenol-F epoxy resin) and theprotective sheet is polyurethane-based (e.g., comprising an aliphaticpolyurethane, such as a polycaprolactone-based aliphatic polyurethaneand/or a polycarbonate-based aliphatic polyurethane). Without beingbound by any particular theory, it is believed that any residualisocyanate-functional groups within the polyurethane-based protectivesheet react with hydroxy-functional groups within the matrix material toform strong covalent bonds between the protective sheet and theunderlying composite article. This chemical reaction can be furtherenhanced when the epoxy resin is cured under heat and pressure while inintimate contact with the polyurethane-based protective sheet (e.g., asis typically the case when processed within a mold). Under such in-moldprocess conditions, when the polyurethane-based protective sheet issubjected to relatively high pressure and elevated temperatures, it isbelieved that the polyurethane-based protective sheet exhibitsreversible thermolysis. During thermolysis, a portion of the urethanebonds within the polyurethane-based protective sheet transform tonon-bonded isocyanate-functional and hydroxy-functional groups. Thus,with greater presence of isocyanate functionality during the cure cycle,additional crosslinking of the polyurethane-based protective layer withthe epoxy matrix material occurs.

Yet another direct bonding method involves lamination. Laminationtechniques include those using heat and/or pressure to adhere aprotective sheet to an underlying composite article after the compositearticle has previously been formed (e.g., via a molding process). Assuch, if the matrix material is a thermoset, it will already have beencured prior to bonding of the protective sheet to the composite article.However, under certain conditions, there may still be residualhydroxy-functional or other functional groups remaining in the matrixmaterial to facilitate crosslinking of the matrix material with theprotective sheet as discussed above. In other instances, the nature ofthe direct bonding of the protective sheet is a function of the amountof heat and/or pressure utilized to adhere the protective sheet to thecomposite article.

The protective sheet can be applied to the exterior surface of acomposite article using in-mold, insert-mold, or co-mold processingtechniques. The latter is sometimes referred to in terms of being a“reactive” molding technique.

In an exemplary embodiment, at least one exterior surface of a compositearticle to be protected is integrally formed in the presence of at leastone protective sheet. “Integrally formed” refers to those exteriorsurfaces that are molded or otherwise fabricated in the presence of theprotective sheet such that the two become integrally bonded during suchformation.

When the composite article is molded, the protective sheet can beapplied using in-mold, insert-mold, or co-mold processing techniquesaccording to this exemplary embodiment. When formed in such a manner,beneficial properties associated with the protective sheet beingpositioned on an exterior surface of the composite article aremaximized, as protective sheets and protective coatings adhered usingother methods are generally more prone to failure. In addition, in-mold,insert-mold, and co-mold processing results in manufacturingefficiencies realized by, for example, elimination of processing stepssecondary to composite article formation and elimination of intermediatelayers (e.g., those comprising adhesive bonding materials) andassociated processing steps in many applications.

As discussed above, a wide variety of materials can be used forprotective sheets of the invention. Protective sheets of the inventionare readily adapted for in-mold, insert-mold and co-mold processingtechniques according to knowledge of those skilled in the art.Significant advantages are imparted when using such exemplary methods.For example, protective sheets applied using in-mold and insert-moldprocessing techniques provide processing efficiencies and improvedperformance properties arising from the improved integral bondingbetween the protective sheet and underlying surface as compared tootherwise adhering the protective sheet to the same surface after itsformation. Integral bonds achieved with in-mold and insert-moldprocessing result in the protective sheet being less susceptible toshifting or sliding when a composite article comprising the same is inuse.

Similar enhancements are obtained when protective sheets of theinvention are co-molded with a composite article in applying aprotective sheet to the outer surface thereof. Co-molding, sometimesreferred to as reactive molding, refers to over-molding of a compositearticle with a protective sheet by applying the protective sheet to amolded composite article's surface and then further molding thecomposite article to sufficiently bond the protective sheet to thearticle's surface. As discussed above, as the matrix material of theunderlying composite article cures (e.g., when the matrix materialcomprises a thermoset material), crosslinks form between the surfacebeing cured and the surface of the protective sheet in contacttherewith.

Each suitable processing technique is susceptible to many variations asunderstood by those of ordinary skill in the art. For example, in-moldand insert-mold processing, which involve placement in a mold of aprotective sheet to be integrally bonded with an article being formedwithin the mold, can be done using a variety of composite moldingtechniques. Such molding techniques include compression, bladder, vacuumbag, autoclave, resin transfer molding (RTM), vacuum-assisted RTM, andother similar methods known to those of ordinary skill in the art.

One method of manufacturing composite articles involves the use ofprepreg. “Prepreg” refers to pre-impregnated composite reinforcementmaterial, where the prepreg contains an amount of matrix material usedto bond the reinforcement material together and to other componentsduring manufacture. Unlike RTM methods, compression, bladder, vacuumbag, autoclave, and similar methods typically involve the use of aprepreg containing both the reinforcement material and the matrixmaterial during molding.

With compression, bladder, vacuum bag, autoclave, and similar methodsinvolving the use of prepreg, a protective sheet is first positionedwithin a suitable mold. One or more layers of prepreg are thenpositioned within the mold prior to initiating cure of the prepreg'smatrix material. During such curing, which is often effected using heatand pressure, the protective sheet becomes integrally bonded to at leasta portion of at least one surface of the composite article. According toa particularly preferred embodiment, crosslinks form between theprotective sheet and the prepreg's matrix material during curing.

With RTM, vacuum-assisted RTM, and similar methods, a protective sheetis placed within a mold containing reinforcement material for thecomposite article to be formed. Matrix material is then injected intothe mold to form a composite article of the invention. Those of ordinaryskill in the art are readily familiar with injectable matrix materialsand techniques for their use in injection molding. The matrix materialitself is generally heated to, for example, a semi-molten state forinjection molding. The term “semi-molten” means capable of flowing intothe molding area.

Prior to and during injection of the matrix material, the protectivesheet can be stabilized within the mold using any suitable method andapparatus, including the many methods associated with in-molddecoration. Such methods include those using gravity, air pressure,pins, tape, static electricity, vacuum, and/or other suitable means. Inaddition, release agents and other molding components can be used asreadily understood by those skilled in the art.

Although not required, according to one variation of this embodiment,the protective sheet is heated prior to injecting the matrix materialinto the mold and against the backside of the protective sheet. Forexample, one variation of this embodiment relates to insert-moldprocessing. During insert-mold processing, as compared to in-moldprocessing, the protective sheet is thermoformed into athree-dimensional shape prior to injection of the matrix material.Typically, the protective sheet is shaped to approximate the contour ofthe interior surface of the mold into which it is placed for injectionmolding. In an exemplary embodiment, the thermoforming step occurswithin the mold such that it does not require transfer prior toinjection of the matrix material. During in-mold processing, theprotective sheet changes shape, if at all, upon injection molding of thematrix material.

According to one aspect of this embodiment, any suitable injectionmolding apparatus is used for RTM molding. Typically, such moldingapparatus have one or more orifices for injection of matrix materialinto the mold. According to RTM and similar methods, with the moldclosed, uncured matrix material (e.g., thermoset resin) is injected intothe mold, after which it flows into interstices within the reinforcementmaterial under heat and pressure while curing. Pressure from injectingmatrix material into the mold combined with the temperature within themold and the surface of associated mold parts causes the matrix materialto fuse together with or bond to the interior surface of the protectivesheet (i.e., it becomes integrally bonded).

In an exemplary method of the invention, vacuum bag processingtechniques are used to integrally bond protective sheets through in-moldprocessing. During vacuum bag processing, a prepreg assembly iscompacted against a mold surface while a vacuum is pulled across theentire assembly and mold to remove excess air, matrix material, or othervolatiles from the assembly. While the vacuum is being pulled, the moldis heated to cure the matrix material of the prepreg. According to apreferred embodiment, the vacuum itself provides all the pressurenecessary to effect full cure of the matrix material.

FIG. 1 is a cross-sectional representation of an exemplary vacuum bagin-mold processing configuration for application of protective sheets102 of the invention. Although the protective sheet 102 is illustratedas a single layer, as discussed above, the protective sheet may actuallyconsist of multiple layers. The protective sheet 102 is placed againstthe surface of the mold 104. As known in the art, the mold 104 mayoptionally have a release agent applied to its surface in order toassist with removal of the final composite article from the mold 104after the in-mold process is complete. On the opposite side ofprotective sheet 102, one or more layers of prepreg 106 are positionedin contact with the protective sheet 102. On the opposite side of theprepreg 106, a peel ply release layer 108 is positioned. The peel plyrelease layer 108 is typically porous or perforated to allow excessmatrix material from the prepreg 106 to flow out of and to be removedfrom the composite article. Opposite the peel ply release layer 108, ableeder fabric layer 110 is positioned to absorb excess resin flowingthrough the peel ply release layer 108. Opposite the bleeder fabriclayer 110, a separator release layer 112 is positioned to prevent excessresin from flowing into an adjacent breather fabric layer 114. Theseparator release layer 112 is often perforated to provide an airchannel for the vacuum into the breather fabric layer 114. The breatherfabric layer 114 is positioned opposite the separator release layer 112and wraps around the other layers to extend to the vacuum nozzle port116. The breather fabric layer 114 provides an air channel from thecomposite article to the vacuum nozzle port 116. The entire assembly issealed within a vacuum by using sealant 120 to seal a vacuum baggingfilm 118 against the surface of the mold 104. By operatively coupling avacuum pump (not shown) to the vacuum nozzle port 116, air can beremoved from within the entire vacuum bag assembly. This compresses thevacuum bagging film 118 against all other layers in the assembly toexert pressure against the surface of mold 104. A vacuum of betweenabout 81 kPa to about 91 kPa (about 24 inches mercury to about 27 inchesmercury) is typically pulled. Once the vacuum is pulled, the entire moldand vacuum bag assembly is placed into an oven (or otherwise heated) tocure the matrix material of the prepreg 106. The temperatures used tocure the matrix material will depend upon the specific matrix materialutilized in the prepreg. Exemplary heating times range from about 30minutes to about 2 hours.

EXAMPLES

Exemplary embodiments and applications of the invention are described inthe following non-limiting examples and related testing methods.

Tensile Testing Method

For tensile testing, samples were formed into standard tensile testingspecimens according to ASTM D638-95 using designations for Type IImeasurements. Tensile testing was performed according to ASTM D638-95.The rate at which the jaws holding the specimen were pulled in a tensilemanner was 1.0 millimeter/minute (0.04 inch/minute) to measure theelastic modulus of the sample, but increased to 300 millimeters/minute(11.8 inches/minute) to obtain the ultimate tensile strength andelongation data. Test data using this method is reported in Table 1.

Recovery Testing Method

For recovery testing, a generally rectangular sample having an initiallength of 25 centimeters (10 inches) and width of 5 centimeters (2inches) was prepared. The sample was stretched in tension until itslength exceeded its initial length by a predetermined percentage (25% or50%). After recovery equilibrium was obtained (approximately 5-10minutes), the length of the relaxed sample was measured and the samplewas qualitatively analyzed for defects or deformation. The change inlength of the sample as compared to the initial length is reported asits “Percent Deformation” in Table 2. Note that values reported in Table2 have a standard deviation of about plus/minus 0.6%.

Elongation Force Testing Method

Force required to elongate a generally rectangular sample having aninitial length of 12.5 centimeters (5 inches) and width of 5 centimeters(2 inches) was measured using an IMASS SP2000 slip/peel tester(available from IMASS, Inc. of Accord, Mass.) operating at a speed of 30centimeters/minute (12 inches/minute). Two forces were measured for eachsample, those being that required to elongate the sample to 125% of itsinitial length and that required to elongate the sample to 150% of itsinitial length. The forces so measured are also reported in Table 2.

Weathering Testing Method

Where indicated, samples were tested for weathering resistance using awell-known QUV test method and weatherometer. The weathering conditionswere as set forth in ASTM D4329.

Example 1

An extensible polyurethane-based protective sheet was prepared such thatthe sheet comprised a carrier layer having a thickness of 150 microns, atopcoat layer having a thickness of 18 microns, and an adhesive layerhaving a thickness of 60 microns. The adhesive layer was adhered to theopposite side of the carrier layer from the topcoat layer. A standardrelease liner was positioned exterior to the adhesive layer, but wasremoved prior to testing.

To prepare the sheet, first a 98# polyethylene-coated kraft paper withsilicone coated on one side was used as a release liner onto which theadhesive layer was formed. The adhesive layer was formed from anadhesive composition prepared by charging a closed vessel with initialcomponents as follows: 20% by weight 2-ethyl hexyl acrylate, 5% byweight methyl acrylate, 1% by weight acrylic acid, 37% by weight ethylacetate, 7% by weight isopropyl alcohol, 26.1% by weight toluene, and3.75% by weight n-propanol. The weight percentages of each componentwere based on total weight of the reaction components, which alsoincluded 0.15% by weight benzoyl peroxide (98%) added in partialincrements. To the initial components, 10% by weight of the benzoylperoxide was first added. Then, the components were charged under anitrogen atmosphere and using agitation. The vessel was heated at 80° C.until exotherm was reached. The exotherm was maintained by addition ofthe remaining benzoyl peroxide. After the benzoyl peroxide was depletedand the exotherm was complete, aluminum acetal acetonate was added tothe polymerized solution in the amount of 0.4% by weight based on solidweight of the polymer.

This adhesive composition was coated onto the release liner and dried ina 14-zone oven, at 20 seconds per zone, with the zone temperatures setas follows: zone 1 (50° C.), zone 2 (60° C.), zone 3 (70° C.), zone 4(80° C.), zone 5 (90° C.), zone 6 (90° C.), zones 7-10 (100° C.), andzones 11-14 (120° C.). With drying, the aluminum acetal acetonatefunctioned to crosslink the polymer. The thickness of the adhesive layerthus formed was 60 microns. The construction was then run through achill stack to reduce the temperature to about 30° C.

A 150-micron-thick film of extruded aliphatic polyurethane, availablefrom Stevens Urethane under the trade designation, SS-2219-92, was thenprovided and laminated to the exposed adhesive layer. This furtherconstruction was run through the 14-zone oven and then again chilled toabout 30° C.

Meanwhile, an 18-micron-thick film for the topcoat layer was formed on a76-micron thick (3-mil-thick) silicone-coated polyester carrier film.The film was formed by solution coating the polyurethane-basedcomposition described below on the supporting carrier film. After thecomposition was coated on the carrier film, it was run through the14-zone oven and then chilled to about 30° C.

The polyurethane-based composition was prepared by charging a closedvessel with 7.36% by weight of a hybrid linear hexanediol/1,6-polycarbonate polyester having terminal hydroxyl groups, 43.46%by weight toluene, 43.46% by weight isopropyl alcohol, and 0.03% byweight dibutyl tin laureate. The weight percentages of each componentwere based on total weight of the reaction components, which alsoincluded 5.68% by weight isophorone diisocyanate added later. Thecomponents were charged under a nitrogen atmosphere and using agitation.After the vessel was heated to 90° C., 5.68% by weight isophoronediisocyanate was continually added to the vessel through the resultantexotherm. After the exotherm was complete, the composition wasmaintained at 90° C. for one additional hour while still usingagitation.

Once the topcoat layer was thus formed, it was thermally bonded to theexposed surface of the carrier layer. During thermal bonding, thecarrier layer and the topcoat layer were contacted for about threeseconds with application of heat 150° C. (300° F.) and 140 Pa (20 psi)pressure. Prior to testing, the release liner and carrier film wereremoved.

All of the individual components used in preparation of the protectivesheet are readily available from a variety of chemical suppliers such asAldrich (Milwaukee, Wis.) and others. For example, the isopropyl alcoholand toluene can be obtained from Shell Chemicals (Houston, Tex.).

Samples of the protective sheet were then tested according to theTensile Testing Method, Recovery Testing Method, and Elongation ForceTesting Method described above. Test data is reported in Table 1.Further, samples of the protective sheet were tested according to theWeathering Testing Method described above. After weathering for 500hours, no visible yellowing was observed by the unaided human eye.Finally, samples of the protective sheet were tested for deglossing byplacing them in an outside environment in the states of Florida andArizona for approximately one year. After one year, no visibledeglossing was observed by the unaided human eye.

TABLE 1 Ultimate Test Tensile Elastic Elongation Temperature StrengthModulus at Break (° C./° F.) (MPa/psi) (MPa/psi) (%) 24/75 58.4/8,46061/8,800 390

TABLE 2 Force Required to Force Required to Percent Elongate to 125%Percent Elongate to 150% Deformation Initial Length Deformation InitialLength After 25% (Newtons/pounds- After 50% (Newtons/pounds- Elongationforce) Elongation force) −0.3 6.1/1.4 −0.6 18.9/4.3

Examples 2A-2C

For each fiber-reinforced composite, a woven carbon fiber fabriccontaining about 3K tow-weight carbon fiber is used. Such fibers andfabric are available from a variety of commercial suppliers, includingA&P Technologies (Cincinnati, Ohio), Fabric Development, Inc.(Quakertown, Pa.), and Textile Products, Inc. (Anaheim, Calif.). Foreach of Examples 2A-2C, a different uncured epoxy resin composition isused to impregnate the woven carbon fiber fabric. Formulation of theepoxy resin composition for each of Examples 2A-2C is described furtherbelow.

After preparation of the epoxy resin composition and hand impregnationof the woven carbon fiber fabric therewith, four layers of the nowimpregnated “prepreg” carbon fiber fabric are stacked upon one another.

As an outer layer, a 150-μm (0.006-inch) thick film of apolycaprolactone-based, aliphatic thermoplastic polyurethane film(available from Argotec, Inc. of Greenfield, Mass.) is positioned on topof the four stacked layers of prepreg carbon fiber fabric. The resulting5-layer structure is then placed into a heated platen press for a periodof about 45 minutes, at a temperature of about 120° C. (250° F.) and anapplied pressure of about 0.34 MPa (50 psi). During this step, the epoxyresin composition is cured. The sample is then removed from the platenpress and allowed to cool.

Any suitable epoxy resin composition can be used in this process. Anumber of commercial suppliers and published documents provideformulation guidelines for epoxy resin systems (e.g., “EPON® ResinChemistry” published by Resolution Performance Products). MostBisphenol-A and Bisphenol-F epoxy resins are expected to be suitable foruse as the epoxy resin according to these Examples 2A-2C. Mostamine-curing agents are expected to be suitable for use therein as well.

Resin Formulation 2A

As recommended in the company's data sheet for Amicure CG-1200 (an aminecuring agent available from Air Products and Chemicals, Inc. ofAllentown, Pa.), a suitable epoxy resin formulation is as follows:

Amicure CG-1200, in the amount of 4-15 phr (parts per hundred weightepoxy resin), is added to an epoxy resin having an epoxide equivalentweight (EEW) of 190. Numerous examples of Bisphenol-F and Bisphenol-Aepoxy resins with an EEW of approximately 190 are commerciallyavailable, including for example, EPON Resin 828 (a Bisphenol-A epoxyresin available from Resolution Performance Products of Houston, Tex.).

Resin Formulation 2B

As recommended in the company's data sheet for Amicure UR (an aminecuring agent available from Air Products and Chemicals, Inc. ofAllentown, Pa.), a suitable epoxy resin formulation is as follows:

Amicure CG-1200 (an amine curing agent available from Air Products andChemicals, Inc. of Allentown, Pa.), in the amount of 6 phr, is added toan epoxy resin having an EEW of 190. Numerous examples of Bisphenol-Fand Bisphenol-A epoxy resins with an EEW of approximately 190 arecommercially available, including for example, EPON Resin 828 (aBisphenol-A epoxy resin available from Resolution Performance Productsof Houston, Tex.). In addition, Amicure UR cure accelerator (asubstituted urea-based accelerator available from Air Products andChemicals, Inc. of Allentown, Pa.) is added in the amount of 2 phr.

Resin Formulation 2C

As recommended in the company's data sheet for Ancamine 2441 (a modifiedpolyamine curing agent available from Air Products and Chemicals, Inc.of Allentown, Pa.), a suitable epoxy resin formulation is as follows:

Ancamine 2441 in the amount of 5 phr, is added to an epoxy resin havingan EEW of 190. Numerous examples of Bisphenol-F and Bisphenol-A epoxyresins with an EEW of approximately 190 are commercially available,including for example, EPON Resin 828 (a Bisphenol-A epoxy resinavailable from Resolution Performance Products of Houston, Tex.). Inaddition, Amicure CG-1200 (an amine curing agent available from AirProducts and Chemicals, Inc. of Allentown, Pa.), in the amount of 6 phr,is added to the epoxy resin.

Example 3

Several layers of carbon fiber prepreg were prepared by hand-coatingsufficient epoxy thermoset resin into a 12K woven carbon fiber fabric.The epoxy resin formulation was prepared based on 100 phr of EPON 863 (aBisphenol-F epoxy resin available from Resolution Performance Productsof Houston, Tex.), 22.4 phr of Ancamine 2441 (a modified polyaminecuring agent available from Air Products and Chemicals, Inc. ofAllentown, Pa.), and 5 phr of CAB-O-SIL TS-720 (a treated fumed silicaavailable from Cabot Corporation of Billerica, Mass.). A protectivesheet was directly bonded to the resulting epoxy-carbon fiber compositearticle using in-mold vacuum bag processing. The protective sheetconsisted of a 150-μm (0.006-inch) thick film of apolycaprolactone-based, aliphatic thermoplastic polyurethane film(available from Argotec, Inc. of Greenfield, Mass. under the tradedesignation ARGOTEC 49510).

A flat aluminum plate was used as a vacuum bag mold surface. Prior toconfiguring a vacuum bag assembly thereon, the aluminum plate wascleaned and treated with the Waterworks Aerospace Release Systemavailable from Waterworks of East Ellijay, Ga. The vacuum bag assemblywas constructed utilizing the following material components: VacuumBagging Film (a modified nylon blue vacuum bagging film available fromThe Composites Store, Inc. of Tehachapi, Calif.), Sealant Tape(available from The Composites Store, Inc. of Tehachapi, Calif. underthe description “Yellow Super Seal Tacky Tape”), Breather Fabric(non-woven polyester fabric available from Richmond Aircraft Products,Inc. of Norwalk, Calif. under the trade designation, A 3000), SeparatorRelease Film (perforated, violet FEP fluorocarbon release film availablefrom Richmond Aircraft Products, Inc. of Norwalk, Calif. under the tradedesignation, A5000 Release Film), Bleeder Fabric (non-woven polyesterfabric available from Richmond Aircraft Products, Inc. of Norwalk,Calif. under the trade designation, A 3000), and Peel Ply Release Film(PTFE-coated fiberglass fabric available from Airtech International,Inc. of Huntington Beach, Calif. under the trade designation, RELEASEEASE 234TFP).

The protective sheet was placed adjacent the aluminum plate. Then, fourapproximately 8-cm×13-cm (3-in×5-in) layers of the 12K carbon fiberprepreg were stacked on the protective sheet for processing in thevacuum bag assembly. After assembly of the vacuum bag system wascomplete, a vacuum was pulled on the prepreg stack for about 10 minutesto compress the various layers. While still pulling the vacuum, theentire assembly was placed into an oven at 120° C. (250° F.) for 60minutes to cure the epoxy resin.

After cooling, the resulting carbon fiber composite articles wereremoved. Upon visual inspection, it was noted that the protective sheetwas intimately bonded to the carbon fiber composite article. Surfacefinish of the protective sheet mirrored that of the aluminum plate.

Example 4

Two layers of carbon fiber prepreg braid were prepared by hand coatingsufficient epoxy thermoset resin into a 3K-braided carbon fiber sock.The epoxy resin formulation was prepared based on 100 phr of EPON 863 (aBisphenol-F epoxy resin available from Resolution Performance Productsof Houston, Tex.), 22.4 phr of Ancamine 2441 (a modified polyaminecuring agent available from Air Products and Chemicals, Inc. ofAllentown, Pa.), and 5 phr of CAB-O-SIL TS-720 (a treated fumed silicaavailable from Cabot Corporation of Billerica, Mass.). A protectivesheet was directly bonded to the resulting epoxy-carbon fiber compositearticle using a bladder molding process. The protective sheet consistedof a single layer of 0.35-mm (0.014-inch) aliphatic polyurethane film(available from Argotec, Inc. of Greenfield, Mass. under the tradedesignation ARGOTEC 49510).

The tubular cavity of a two-piece aluminum mold was used to define theouter surface of a lacrosse stick shaft to be formed from a compositematerial. The mold was approximately 81 centimeters (32 inches) inlength and approximately 2.5 centimeters (1 inch) in diameter and wasconfigured as an octagonal shape, which is common to lacrosse stickshafts. Prior to configuring the mold assembly, the protective sheet wasapplied to the tubular cavity, which was first coated with FEP releaseagent. An inflatable mandrel was constructed by fixturing a tubularlatex bladder (available from Latex Technology Inc. of San Marcos,Calif.) over a steel tube attached to a supply of pressurized air. Theprepreg braid was placed over the inflatable mandrel and the assemblywas inserted into the mold cavity.

Pressurized air was applied to the inflatable mandrel causing thebladder to inflate and moving the prepreg braid into contact with theprotective sheet against the mold surface. Pressure inside the bladderwas increased to 0.17 MPa (25 psi) in order to compress the layers ofprepreg braid and integrally bond the prepreg braid and the protectivesheet. The mold was heated 5° C. per minute to 120° C., at which pointit was held at 120° C. for 45 minutes to allow the epoxy resin to cure.

After cooling, the resulting carbon fiber composite lacrosse stick shaftwas removed. Upon visual inspection, it was noted that the protectivesheet was integrally bonded to the carbon fiber composite article.Surface finish of the protective sheet mirrored that of the aluminummold.

Various modifications and alterations of the invention will becomeapparent to those skilled in the art without departing from the spiritand scope of the invention, which is defined by the accompanying claims.It should be noted that steps recited in any method claims below do notnecessarily need to be performed in the order that they are recited.Those of ordinary skill in the art will recognize variations inperforming the steps from the order in which they are recited.

1. A composite article comprising a protective sheet integrally bondedto at least one portion thereof.
 2. The composite article of claim 1,wherein the composite article comprises a fiber-reinforced compositematerial underlying the protective sheet.
 3. The composite article ofclaim 1, wherein the composite article has at least one exterior surfacecomprising a composite material and wherein the protective sheet fullycovers the exterior surface comprising the composite material.
 4. Thecomposite article of claim 1, wherein the composite article is fullycovered by the protective sheet.
 5. The composite article of claim 1,wherein the composite article comprises at least a portion of amotorized vehicle.
 6. The composite article of claim 1, wherein thecomposite article comprises at least a portion of an aerospacecomponent.
 7. The composite article of claim 1, wherein the compositearticle comprises at least a portion of a sporting implement.
 8. Thecomposite article of claim 1, wherein the composite article comprises atleast a portion of a shaft-based sporting implement.
 9. The compositearticle of claim 7, wherein the sporting implement is selected from agolf club, a bicycle frame, a hockey stick, a lacrosse stick, a skipole, a ski, a fishing rod, a tennis racket, an arrow, a polo mallet,and a bat.
 10. The composite article of claim 9, wherein the sportingimplement comprises a lacrosse stick.
 11. The composite article of claim9, wherein the sporting implement comprises a ski pole.
 12. Thecomposite article of claim 9, wherein the sporting implement comprises ahockey stick.
 13. The composite article of claim 1, wherein at least oneexterior surface of the composite article to be protected is integrallyformed in the presence of the protective sheet.
 14. The compositearticle of claim 1, wherein the protective sheet is extensible.
 15. Thecomposite article of claim 1, wherein the protective sheet comprises atleast one elastomeric material.
 16. The composite article of claim 15,wherein the elastomeric material is based on polyurethane, ionomer, orfluoroelastomer chemistry.
 17. The composite article of claim 1, whereinthe protective sheet comprises at least one polyurethane-based layer.18. The composite article of claim 17, wherein the polyurethane-basedlayer comprises at least one aliphatic-based polyurethane.
 19. Thecomposite article of claim 18, wherein the aliphatic-based polyurethaneis selected from polyether-based aliphatic polyurethane, polyester-basedaliphatic polyurethane, polycaprolactone-based aliphatic polyurethane,and polycarbonate-based aliphatic polyurethane.
 20. The compositearticle of claim 1, wherein the composite article is based on at leastone thermoplastic resin.
 21. The composite article of claim 1, whereinthe composite article is based on at least one thermoset resin.
 22. Thecomposite article of claim 1, wherein the composite article is based onat least one epoxy resin.
 23. The composite article of claim 22, whereinthe epoxy resin is selected from a Bisphenol-A epoxy resin and aBisphenol-F epoxy resin.
 24. The composite article of claim 1, whereinthe composite article is based on at least one epoxy resin and theprotective sheet comprises at least one polyurethane-based layer. 25.The composite article of claim 1, wherein at least a portion of theprotective sheet is crosslinked with at least a portion of the compositearticle.
 26. A method of applying a protective sheet to at least aportion of an exterior surface of a composite article, the methodcomprising: providing the protective sheet prior to forming the exteriorsurface of the composite article; and integrally forming the exteriorsurface of the composite article in the presence of the protective sheetsuch that at least a portion of the exterior surface of the compositearticle and the protective sheet become integrally bonded.
 27. Themethod of claim 26, wherein the exterior surface of the compositearticle is formed using an in-mold processing or insert-mold processingtechnique.
 28. The method of claim 26, wherein the exterior surface ofthe composite article is formed using a vacuum bag processing technique.29. The method of claim 26, wherein the exterior surface of thecomposite article comprises a fiber-reinforced composite material priorto application of the protective sheet to at least a portion thereof.30. The method of claim 26, wherein the protective sheet undergoesthermolysis during cure of the composite article.
 31. A method ofapplying a protective sheet to at least a portion of an exterior surfaceof a composite article, the method comprising: providing the protectivesheet; forming the exterior surface of the composite article; andco-molding the protective sheet to the exterior surface of the compositearticle such that at least a portion of the exterior surface of thecomposite article and the protective sheet become integrally bonded. 32.The method of claim 31, wherein the exterior surface of the compositearticle comprises a fiber-reinforced composite material.
 33. A compositearticle comprising an exterior protective sheet adhered to an underlyingcomposite material surface, wherein the composite article is essentiallyfree of additional layers between the protective sheet and theunderlying composite material surface.
 34. The composite article ofclaim 33, wherein the composite article comprises printed material on atleast one outwardly visible surface thereof.
 35. The composite articleof claim 33, wherein the composite material comprises a fiber-reinforcedcomposite.
 36. A composite article comprising a protective sheet adheredto at least one exterior portion thereof, wherein the protective sheetis capable of providing all desired enhancements in performance andaesthetic properties of the composite article in one protective sheetcomponent as compared to use of multiple protective sheet or protectivecoating components.